The present invention relates to a method and apparatus for detecting an exchange period for parts within an electrophotographic printing apparatus, and more particularly to a control method and apparatus for sensing when a replaceable part within an electrophotographic printing apparatus has received a requisite amount of use and automatically informing a user of such status.
In electrophotographic printing devices, in order to ensure continuous high quality printing, it is highly recommended that certain parts within the device be replaced after a prescribed amount of use. That is, to ensure high quality printing in a LBP (Laser Beam Printer), LED (Light Emitting Diode) printer, duplicator, facsimile, etc., parts such as the photosensitive drum should be replaced after the printing output of the device reaches a prescribed quantity. There are several replaceable parts within an electrophotographic printing device, including the photosensitive drum, developing unit, etc. Timely replacement of these parts improves copy quality and visibility, and also lengthens the operating life of the device.
Many electrophotographic printing devices include equipment for detecting when the useful life of a given replaceable part has been exceeded. That is, many devices utilize mechanical or electronic counters that detect the number of copies that have been produced using a particular replaceable part. When a counter value equals a predetermined replacement value for the particular replaceable part, a corresponding indication is displayed to the user.
One device utilizing such a concept is disclosed in U.S. Pat. No. 5,216,464 entitled Image Forming Apparatus Having Replaceable Element Which Is Replaced Based On Frequency Of Use, issued to Kotani et al. on 1 Jun. 1993. In this effort, an image forming apparatus includes a replaceable element and a predicting apparatus for predicting the amount of operational life remaining in the replaceable element. The predicting apparatus makes its evaluations on the basis of various calculations. Although the disclosed invention claims to make an accurate prediction as to when an element should be replaced, I believe the process can be simplified so that it is more easily implemented in an image forming apparatus.
Another effort directed at this concept is disclosed in U.S. Pat. No. 5,276,461 entitled Electrophotographic Printing Device, issued to Saito on 4 Jan. 1994. Here, an electrophotographic printing device includes a nonvolatile memory for storing data indicative of the printing history of a photosensitive unit. Saito '461 further discloses that the nonvolatile memory is a removable memory card. Since this nonvolatile memory is not integral with the replaceable photosensitive unit, I have observed that a device constrained according to Saito '461 has potential problems because an accurate printing history may not be maintained if the photosensitive unit is reinstalled into another image forming device without the corresponding nonvolatile memory.